It is well known that the action of opiate drugs is mediated through a specific receptor. The localization of these receptors within the CNS to date bas depended solely on the use of autoradiographic techniques. Recent solubilization and purification of the opiate receptor protein has allowed for the generation of polyclonal and monoclonal antibodies directed against the opiate receptor. It is the initial intent of this investigation to further characterize these antibodies as well as develop immunocytochemical procedures for the light microscopic visualization of the opiate receptor. Following the complete elucidation of the distribution of the receptor via these methods, ultrastructural analysis of the receptor will be completed. Light microscopic as well as ultrastructural interactions of the opiate receptor with enkephalin and ACTH/Beta-endorphin will be examined in the CNS with particular emphasis on areas where these peptides have been shown to be involved in control analgesia and autonomic function. Finally, the effects of a developmental central opiocortin deficiency on the light microscopic distribution and ultrastructure of the opiate receptor will be examined.